Beauden Barrett avoids a serious concussion. Photo / Getty Images
A breakthrough study of New Zealand rugby players has, for the first time, concluded a link between the national sport and neurodegenerative disorders.
The retrospective statistical study dubbed Kumanu Tāngata - The Aftermatch Project – is the largest of its kind.
Alongside projecting a higher risk for rugby players of brain disease the report, led by the University of Auckland and funded by World Rugby and the New Zealand Rugby Foundation, has a surprising revelation as to which positions pose greater threat of Alzheimer’s and other dementias.
The study compared 12,861 males who played high-level rugby between 1950 and 2000 with 2,385,543 men from the general population matched by age, ethnicity and birthplace. Female players were not included because of the low number during the period studied.
The Herald has obtained a yet-to-be-peer-reviewed preprint of the 29-page report that provisionally concludes playing high-level rugby is associated with a “slight to moderate” increase in neurodegenerative diseases such as Alzheimer’s and dementia.
The extensive report found a higher percentage of rugby players (4.7 per cent) than the general population (3.9 per cent) developed neurodegenerative diseases. It also states three of the 20 players who developed a neurodegenerative disease each year would not have been expected to if they had not played rugby.
While reports abroad previously purported ties between rugby and brain disease, this study is the first in a New Zealand context.
The report compared health outcomes of first-class players from historian Clive Akers’ New Zealand Rugby Register - featuring 729 former international and professional players and 12,129 who played at provincial or first-class amateur level - with the general population by using Statistics New Zealand’s integrated data.
“We found that former rugby union players were at increased risk of neurodegenerative disease diagnosis compared to males in the general population,” the report states.
This increased risk was observed for Alzheimer’s disease and other dementias but not for Parkinson’s disease or motor neurone disease. Across all neurodegenerative diseases, players who played for six or more years had the greatest risk of disease.
“There was no difference in the rate of neurodegenerative diseases between those who played at a higher level and those who played at a lower level only (provincial/first-class amateur). The magnitude of association between playing rugby and neurodegenerative disease found in this study tended to be smaller than most previous investigations of the association between exposure to contact and collision sports and neurodegenerative disease.”
Surprisingly, given the combative nature of rugby forwards, players in back positions (6066) had greater risks of Alzheimer’s and other dementias than those in the forwards (5253).
The provisional report found the rate of risk onset for Alzheimer’s was 42 per cent higher for rugby players than the general population – and 17 per cent higher for any neurodegenerative disease.
Rugby players were also deemed 28 per cent more at risk to die from a neurodegenerative disease. Other causes of death such as cancer and heart disease were, however, more prevalent among players – and lower than the general population.
“We observed that out of every 1000 men in the general population, 39 died from or were diagnosed with a neurodegenerative disease over the follow-up period,” the report says. “Among former rugby players, the number was 47 per 1000; an extra eight cases per 1000 people over the study period, or approximately three extra neurodegenerative disease cases per year given the size of the player cohort.”
Of the 4.7 per cent of rugby players found to have suffered from neurodegenerative disorders, 30 per cent would not have been expected to have had Alzheimer’s had they not been exposed to high-level rugby. That equates to 48 former players.
The equivalent statistic for diagnoses of other dementias was 14 per cent or 59 players.
As the data for the Kumanu Tāngata report stopped in the year 2000, no accurate judgements can be made about rugby’s post-professionalisation era. It is, however, accepted that athletes have grown increasingly larger and stronger and that collisions are more frequent in the modern New Zealand game that also embraces a vastly greater number of powerful Pasifika players.
University of Auckland researchers declined to comment on the study until it is peer-reviewed but in a statement to the Herald, New Zealand Rugby said player welfare remained one of its highest priorities.
“We are absolutely focused on doing everything we can to keep players as safe as possible from the risks of concussion,” NZ Rugby said.
“We are particularly proud to be involved in world-leading research like Kumanu Tāngata. The project is the largest of its kind ever undertaken and is vital to the future understanding of brain health in rugby. In time, the study will also publish papers which look at other aspects of playing rugby, including the health benefits of playing.
“The Kumanu Tāngata research is currently undergoing an independent peer review process with an international scientific journal that will impact the final published version. It would be improper to comment on the study’s findings until this is complete.”
Compared to previous studies of head impacts in rugby such as that completed by Glasgow University last October, Kumanu Tāngata’s 0.8 per cent increased risk for brain diseases is significantly less. The common theme, though, contributes to a consistent picture of rugby collisions impacting brain health which will strengthen the spotlight on whether the game needs to change.
Last year the Glasgow University paper showed elite rugby players were at 2.7 times more risk of brain disease than the general population. The study revealed rugby players’ risk factor for motor neuron disease was 15 times higher than the general population’s - and suggested the risk of developing Parkinson’s disease was at three times higher.
Researchers found 47 (11.4 per cent) of the former rugby players and 67 (5.4 per cent) of the general population comparison group had an incident-related neurodegenerative disease diagnosis, based on death certification, hospital admission or prescribing information.
That study, however, compiled a much smaller sample size of 412 players resulting in wide confidence intervals around effect estimates for some neurodegenerative diseases.
“NZR is at the forefront of concussion initiatives in both professional and community rugby,” NZ Rugby said. “This includes the blue card, mandatory stand down periods for community players, reducing the tackle height across community rugby, compulsory education for community coaches, head injury assessment protocols and the use of smart mouthguard technology in the professional game, and the 20-year RugbySmart programme with ACC which has seen a significant reduction in playing injuries.”
Rugby is not alone in confronting mounting evidence that strongly suggests its players are at greater risk of neurodegenerative disease than the general population, with other studies abroad indicating the rate of mortality from brain disease increases three or fourfold in former football and American football players.
A study of Swedish football, published last April, found 537 (8.9 per cent) of 6007 male football players and 3485 (6.2 per cent) of 56168 from the general population were diagnosed with neurodegenerative disease.
The New Zealand report comes as a lawsuit is being prepared overseas covering former rugby players left with cognitive issues from post-concussion syndrome to suspected chronic traumatic encephalopathy (CTE). Former All Blacks prop Carl Hayman, who claims rugby exploited him since being diagnosed with dementia, is among that group.
Ongoing debate about links between concussions and CTE, a progressive brain condition, in collision sports can only be proven through autopsy.
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